Recently, a magnesium (hereinafter, Mg) alloy sheet has been used in, for example, housings of cellular phones and laptop computers. Since Mg alloys have poor plastic workability, cast materials produced by die casting or thixomolding are mainly used. In general, such cast materials are subjected to, for example, rolling so as to improve the mechanical properties thereof.
PTL 1 describes that rolling is performed on a cast material composed of a magnesium alloy corresponding to the AZ91 alloy in the American Society for Testing and Materials (ASTM) standards, the cast material being produced by a twin-roll continuous casting process. Specifically, the rolling is performed while respectively controlling a surface temperature of a Mg alloy material sheet immediately before the sheet is inserted into reduction rolls and a surface temperature of the reduction rolls to specific temperatures.